Fire extinguishing aerosol devices generally have a housing with a discharge opening, a charge for producing a fire-extinguishing aerosol, and an ignition unit. When the ignition unit is operated, the pyrotechnic or solid-fuel charge is ignited, and the gaseous combustion products thereof form the fire extinguishing aerosol that passes through the discharge opening into the fire region and extinguishes the fire. In some prior devices, the ignition unit comprises an igniter positioned on or in the pyrotechnic that ignites when electrically activated or heated to a high temperature, such as that caused by a fire. One problem in causing ignition in this manner is that the igniter must be inside the housing, thus requiring that the container itself reach a high temperature prior to ignition.
Another shortcoming is the necessity to connect electrically operated units to suitable detection devices and releasing panels (cost, maintenance, reliability issues.) In some prior devices, a fuse, such as one composed of cordite extends outside of the container. Such fuses, while igniting in response to a desired temperature, are prone to damage and potential malfunction (fuse is limited to one, high activation temperature—significant damage occurs prior to activation). It is also dangerous to ship fire extinguishing devices which can be undesirably activated during shipment.
In one existing device, a bulb is used to hold a spring loaded pin in place. At a prespecified temperature, the bulb breaks, releasing the pin which ignites the pyrotechnic.